# Filling-In of Surface Darkness

M. E. Rudd, & K. F. Arrington*Investigative Ophthalmology & Visual Science*

2000; 41(4). Abstract nr 1185, p. S226

## Abstract

**Purpose:** To study mechanisms of darkness induction in light ofrecent models of surface brightness filling-in. **Methods:** Two subjectsjudged the brightness of a 1.0 cd/m2, 0.9 deg (radius) disk that was surroundedby two concentric annuli (outer radii = 1.8 and 2.7 deg, respectively)of varying luminance. Disk brightness was measured by adjusting the luminanceM of a comparison disk to a achieve a brightness match to the judged disk.The comparison disk was the same size as the judged disk and surroundedby a 5.89 cd/m2, 1.8 deg annulus). Matches were studied as a function ofthe luminances A1 and A2 of the inner and outer surround annuli, underthe constraint that A2 3 A1 3 disk luminance. **Results:** For eachsubject, the brightness matches were quantitatively modeled by the followinglinear regression equation: log M = e1 - e2 log A1 - e3 log2 A1 - e4 logA2 + e5 log A1 log A2. **Conclusions:** We derive a theoretical brightnessmatching equation based on a model of darkness induction by a diffusivefilling-in process and show that this equation has the same form as theempirical brightness matching equation. The theory is used to extract underlyingparameters of the underlying neural filling-in mechanism--such as the percentageof the diffusing surface signal that is stopped by a border as a functionof the border contrast--from the coefficients of the brightness matchingequation that were estimated from the linear regression analysis of thedata.

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